For increasing productivity, multiple processes are integrated to cutting processes of workpieces. One possibility is the combination of turning and milling operations in one machine. This machine typically comprises a rotary table that is supported so that it can rotate via a corresponding rotary table bearing assembly. While up until now rotary table bearing assemblies were designed only for swiveling tasks or slow continuous turning, with respect to the extension of the scope of work, it is required to design the bearing assembly so that high rotational speeds can also be realized for a longer time period. To do this, the rotary table bearing is typically constructed as a compact bearing and a torque motor is used as a drive. For higher rotational speeds, the rotary table bearing is constructed as a rolling bearing, wherein different constructions can be used, tailored to the loading of the bearing. The performance capacity of the bearing is determined by the effective pretensioning that equals a few micrometers depending on the bearing diameter in the rolling contact. According to the friction in the rolling contact, at high rotational speeds, friction losses occur in the form of heat that is discharged to the inner ring and the outer ring.
The torque motor that is used must provide a limited rotational speed that is usually achieved only by a field-weakening operation in order to still have sufficient torque for the milling process in the lower rotational speed range. At high rotational speeds of the rotor, the current control frequencies are also high, which in turn leads to high losses from magnetization changes. This in turn leads to an increased generation of heat and the rotor becomes hot due to the losses from magnetization changes in the rotor. Active cooling of the rotor is possible only with increased expense due to the risk of leakage. In known constructions, the rotor is connected to the shaft that is connected to the inner ring and is supported so that it can rotate by the inner ring and carries the table. This results in heat transfer from the rotor to the rotary table bearing. Due to the preferred use of grease lubrication in the rotary table bearing, heat dissipation via the lubricant is not guaranteed. Heat sources and heat sinks produce local temperature gradients that usually heat the stationary and moving parts of the rotary table differently. Due to the heat transfer from the rotor via the bearing inner ring to the table plate, a heat concentration in the radial part of the bearing is given. This has the result that the shaft and the inner ring expand more than the outer ring, wherein the pretensioning and the pressure in the rotary table bearing, especially the radial raceway, increase, which reduces the service life.